1. Field of the Invention
The present invention relates to a dual type unitary air conditioner, and more particularly to a method for controlling the amount of a refrigerant of a dual type unitary air conditioner using a centralized heating and cooling system and an individual heating and cooling system so that the appropriate amount of a refrigerant is supplied to an individual warm and cold air circulator under the condition that the supercooled state of the refrigerant having passed through the individual warm and cold air circulator and the overloaded state of the individual warm and cold air circulator are prevented.
2. Description of the Related Art
Generally, a unitary air conditioner is a type of centralized heating and cooling system, which generates hot air or cool air using a heating and cooling unit installed in a basement of a building, such as a factory, an office, a hotel, or a house, and transfers the air to individual spaces through ducts installed in a wall of the building.
The unitary air conditioner has zone controllers installed in the ducts for divisionally independently supplying warm or cold air to regions required to be heated and cooled and regions not required to be heated and cooled, or a plurality of heating and cooling units independently installed in proportion to the number of the regions.
FIG. 1 is a schematic view of a conventional unitary air conditioner, FIG. 2 is a circuit diagram of the conventional unitary air conditioner, FIG. 3 is a schematic view of another conventional unitary air conditioner, and FIG. 4 is a circuit diagram of the conventional unitary air conditioner.
As shown in FIGS. 1 and 2, a conventional unitary air conditioner comprises one outdoor unit 1 fixedly installed at the outside of a building (a two-story house in the drawings), a warm and cold air circulator 2 connected to a first heat exchanger 1b of the outdoor unit 1 and fixedly installed in a basement or an outbuilding of the building, an air supply duct 3 and an air discharge duct 4 respectively connected to an air supply hole and an air discharge hole of the warm and cold air circulator 2 and divisionally buried in a wall of each of stories of the building, and zone controllers 5a˜5d installed in the air supply duct 3 and the air discharge duct 4 for controlling air supplied to each of the stories and air discharged from each of the stories.
The outdoor unit 1 comprises at least one compressor 1a installed in a case for compressing a refrigerant gas, the first heat exchanger 1b connected to the compressor 1a by a refrigerant pipe for condensing the refrigerant gas (in a cooling mode) or absorbing latent heat (in heating mode), an expansion device 1c for decompressing and expanding the refrigerant gas, and an outdoor fan (not shown) for supplying external air to the first heat exchanger 1b to increase the heat exchange capacity of the first heat exchanger 1b. 
The warm and cold air circulator 2 comprises a second heat exchanger 2a installed in a case and having one end connected to the first heat exchanger 1b and the other end connected to the expansion device 1c, and an air supply fan (not shown) located at the lower stream of the second heat exchanger 2a for guiding warm air or cold air to the air supply duct 3. The case of the warm and cold air circulator 2 has an air channel having an approximately U shape so that the second heat exchanger 2a and the air supply fan (not shown) are installed in the air channel. The air supply duct 3 is connected to an air supply hole of the air channel, and the air discharge duct 4 is connected to an air discharge hole of the air channel.
As described above, the air supply duct 3 and the air discharge duct 4 are respectively connected to the air supply hole and the air discharge hole of the warm and cold air circulator 2, and are divisionally branched into unit ducts buried in corresponding regions Z1 and Z2. Discharge ports 3a for supplying warm air or cold air to the corresponding regions Z1 and Z2, and intake ports 4a for sucking internal air for circulation are respectively formed through the unit ducts of the air supply duct 3 and the air discharge duct 4.
The zone controllers 5a˜5d are valves installed in the unit ducts of the air supply duct 3 and the air discharge duct 4 buried in the corresponding regions Z1 and Z2 so that warm air or cold air can be divisionally supplied to the corresponding regions Z1 and Z2. The zone controllers 5a˜5d are connected to a controller (not shown) and are automatically manipulated so that the zone controllers 5a˜5d can be switched on/off by detecting temperatures or humidities of the corresponding regions Z1 and Z2 and comparing the detected temperatures or humidities to predetermined values, or are manually manipulated.
The above heat pump-type unitary air conditioner having the zone controllers 5a˜5d will be operated as follows.
That is, in a two-story house, loads of respective stories (the corresponding regions) Z1 and Z2 are detected. When it is determined that both the detected loads of the respective stories Z1 and Z2 are more than a predetermined value, the unit ducts of the air supply duct 3 simultaneously supply warm air or cold air to the respective stores Z1 and Z2, and when it is determined that one of the detected loads of the respective stories Z1 and Z2 is more than the predetermined value, the corresponding unit duct of the air supply duct 3 supplies warm air or cold air to the story Z1 or Z2.
For example, in a cooling mode, the compressor 1a of the outdoor unit 1 is driven to compress the refrigerant gas into a high-temperature and high-pressure state, and the refrigerant gas is condensed into a high-temperature and high-pressure liquid state by the first heat exchanger 1b of the outdoor unit 1, is converted into a low-temperature and low-pressure state by the expansion device 1c of the outdoor unit 1. Then, the refrigerant passes through the second heat exchanger 2a of the warm and cold air circulator 2 so that the refrigerant gas exchanges heat with air sucked into the air channel through the air discharge duct 4, thereby generating cold air. The cold air is supplied to the air supply duct 3 through an inlet of the air supply fan (not shown). Here, when all the loads of the respective stories Z1 and Z2 are more than the predetermined value, the zone controllers 5a˜5d, which are automatically manipulated, are opened by the controller, or the zone controllers 5a˜5d, which are manually manipulated, are opened by the manipulation of a user. Thereby, the cold air generated by the warm and cold air circulator 2 is supplied to the respective unit ducts of the air supply duct 3, and is converted into a gaseous state by evaporation, thus cooling the respective stories Z1 and Z2. on the other hand, when one of the loads of the respective stories Z1 and Z2 is less than the predetermined value, the zone controllers 5a˜5d, which are installed in the story Z1 or Z2, the load of which is not less than the predetermined value, are automatically or manually opened. Thereby, the cold air is supplied only to the unit ducts of the air supply duct 3 installed in the corresponding story Z1 or Z2, thus cooling the corresponding story Z1 or Z2.
The operation of the heat pump-type unitary air conditioner having the zone controllers 5a˜5d in a heating mode is the same as that in the cooling mode except that the circulation of the refrigerant in the heating mode is performed in the reverse order according to a heat pump-type refrigerating cycle.
The above conventional unitary air conditioner having the zone controllers 5a˜5d selectively supplies warm air or cold air according to a variation of the temperatures of the corresponding regions Z1 or Z2 using one indoor unit 1, thus reducing a power consumption rate. However, the above unitary air conditioner has a difficulty in installing new zone controllers in the air supply duct 3 and the air discharge duct 4 when an additional warm and cold air circulator is installed in a space having a high load (for example, a kitchen, an attic, or an exercise chamber). Further, the above unitary air conditioner is operated using a centralized heating and cooling system and thus has a limit in the capacity of the warm and cold air circulator 2, thereby causing a deterioration of efficiency.
In view of the above problem, FIGS. 3 and 4 illustrate another conventional unitary air conditioner. This unitary air conditioner does not comprise zone controllers, but comprises a plurality of outdoor units and a plurality of warm and cold air circulators independently installed according to the respective regions Z1 or Z2.
That is, the above unitary air conditioner comprises a first outdoor unit 11, a first warm and cold air circulator 12, a first air supply duct 13, and a first air discharge duct 14, which are used to heat and cool a first story of a two-story house, and a second outdoor unit 21, a second warm and cold air circulator 22, a second air supply duct 23, and a second air discharge duct 24, which are used to heat and cool a second story of a two-story house.
The first outdoor unit 11 comprises a first compressor 11a, a first heat exchanger 11b connected to the first compressor 11a by a four-way valve, and a first expansion device 11c connected to the first heat exchanger 11b. 
The first warm and cold air circulator 12 comprises a third heat exchanger 12a connected to the first expansion device 11c, and a first air supply fan (not shown) installed at the lower stream of the third heat exchanger 12a. 
The second outdoor unit 21 comprises a second compressor 21a, a second heat exchanger 21b connected to the second compressor 21a by a four-way valve, and a second expansion device 21c connected to the second heat exchanger 21b. 
The second warm and cold air circulator 22 comprises a fourth heat exchanger 22a connected to the second expansion device 21c, and a second air supply fan (not shown) installed at the lower stream of the fourth heat exchanger 22a. 
The above independent unitary air conditioner will be operated as follows.
That is, in a cooling mode in a two-story house, when loads of respective stories Z1 and Z2 are more than a predetermined value, the first compressor 11a and the second compressor 21a are simultaneously operated so that the refrigerant is compressed into a high-temperature and high-pressure gaseous state by the first and second compressors 11a and 21a, and the refrigerant is condensed into a high-temperature and high-pressure liquid state by the first heat exchanger 11b and the second heat exchanger 21b. The obtained refrigerant gas is converted into a low-temperature and low-pressure state by the first and second expansion devices 11c and 21c and supplied to the third heat exchanger 12a and the fourth heat exchanger 22a so that the refrigerant gas is evaporated by air introduced through the air discharge ducts 14 and 24 of the first and second warm and cold air circulators 12 and 22, thereby generating cold air. The cold air is supplied to the first air supply duct 13 and the second air supply duct 23 through the first air supply fan (not shown) and the second air supply fan (not shown), and is supplied to the respective stores Z1 and Z2 through the first and second air supply ducts 13 and 23, thereby cooling the respective stores Z1 and Z2. Then, the air is repeatedly circulated to the warm and cold air circulators 12 and 22 through the first and second discharge ducts 14 and 24 of the stores Z1 and Z2.
The operation of the above unitary air conditioner in a heating mode is the same as that in the cooling mode except that the circulation of the refrigerant in the heating mode is performed in the reverse order according to a heat pump-type refrigerating cycle.
The above conventional unitary air conditioner does not require zone controllers in the first and second air supply and discharge ducts 13, 23, 14, and 24, thus being easily installed and controlled. Further, this conventional unitary air conditioner independently heats and cools the regions Z1 and Z2, thus having excellent efficiency. However, the above unitary air conditioner has a difficulty in installing an additional warm and cold air circulator in a space having a high load. Further, the above unitary air conditioner has the outdoor units 11 and 21 independently installed in the regions Z1 and Z2, thus increasing production costs.
In order to maintain control temperatures in the respective regions, i.e., indoor temperatures, to a predetermined temperature desired by a user, it is necessary to control the operation capacity of the compressors of the above two conventional unitary air conditioners corresponding to the total load amounts of the respective regions and to control the amount of the refrigerant passing through the respective indoor heat exchangers by adjusting the opening degrees of the electric valves.